I need to come up with a way to upload and overwrite and existing image file from a dynamically generated list. For instance, there would be a drop-down select box with Company A, Company B, Company C, etc. and when the user selects one of them it should display a prompt to upload a new logo image file, overwriting the existing logo file. Any help would be appreciated.
I'm not sure why you need a prompt. Sounds like an unnecessary annoyance to me.
A simple form with a select and input type="file" should get you started. Then I would probably do something like:
1. upload the file to a temp folder on your server.
2. Rename it according to what company was selected.
3. Move it to it's permanent folder.